Both women are Prison Service employees and are tasked with overseeing education programmes at Maghaberry in Co Antrim.

The source added: “Teaching is very lucrative within the service.

“Many earn between £55 and £70 an hour.

“They come in to teach in the evenings and can even claim mileage from home and back. It is pretty easy money.” When asked about the claims a Prison Service spokesman said: “We do not comment on staffing issues.”

Maguire, 49, was convicted of murdering David “Digger” Barnes in North Belfast.

The 39-year-old was shot as he lay in bed beside his girlfriend after the gunman broke into the flat at Brookvale Avenue.

Maguire, with a previous address at Whinpark Road in Newtownards, Co Down, was said to have carried out the shooting on weekend leave while serving a prison sentence for robbery.

In 2006 he received a 24-year term after being convicted of the murder and a separate arson attack on the home of a relative of Mr Barnes.

Maguire launched an appeal against the guilty verdicts in May by claiming the trial was unfair.

The court heard he was not represented for 54 of the 75 days of his hearing. The appeal process is continuing.

Last week a damning report on Maghaberry warned someone could be killed if it does not address flaws in how it’s run.

The independent inspection revealed “significant failures in local leadership combined with an ineffective relationship with senior management within the Northern Ireland Prison Service”.

It added this has contributed to the jail becoming “unsafe and unstable for inmates and staff”.

The findings of the report were jointly published by Brendan McGuigan, chief inspector of Criminal Justice in Northern Ireland, and Nick Hardwick, Her Majesty’s chief inspector of prisons in England and Wales.

Yesterday, Maghaberry’s governor insisted he is confident he can address the concerns.

Phil Wragg was appointed to the post in August – three months after the probe was carried out.

He told the BBC improvements have already been made and he expects a more positive report in January.

Mr Wragg added: “What you have to remember about the inspection is it was a snapshot in time, at a time the establishment was seen to be having a number of particular concerns.

“The words the inspectors used are not how I would describe Maghaberry today. Reports of that nature are something no prison governor ever wants to see about his or her establishment.

“But we as a service are working together to ensure establishments operate to the required high performance standard.”